Armstrong Siddeley Mongoose

The Armstrong Siddeley Mongoose is a British five-cylinder radial aero engine produced by Armstrong Siddeley. Developed in the mid-1920s it was used in the Hawker Tomtit trainer and Parnall Peto seaplane amongst others. With a displacement of 540 cubic inches (9 litres) the Mongoose had a maximum power output of 155 horsepower (115 kilowatts).

Armstrong Siddeley Mongoose fitted to the Shuttleworth Collection's airworthy Hawker Tomtit
Type Radial engine
National origin United Kingdom
Manufacturer Armstrong Siddeley
First run 1926
Major applications Hawker Tomtit
Avro 504N
Developed into Armstrong Siddeley Serval

A Mongoose engine powers the sole remaining airworthy Hawker Tomtit, based at Old Warden.

Design and development

The Mongoose is a five-cylinder, single-row, air-cooled radial piston engine. The engine features twin forward-mounted ignition magnetos and enclosed valve rockers, the cylinders being the same as those used for the earlier Jaguar engine.[1] An unusual feature of the Mongoose is the vertical position of the lower cylinder, a design thought likely to promote oil fouling of the spark plugs.[2]

Built in several variants, power output ranged between 135 and 155 hp (100-115 kW).


Mongoose I
1926, 135 hp.
Mongoose II
1930, 155 hp.
Mongoose III
Mongoose IIIA
1929, civil use.
Mongoose IIIC
1929, Military use based on IIIA.




An Armstrong Siddeley Mongoose IIIC powers the sole remaining airworthy Hawker Tomtit, K1786/G-AFTA, owned and operated by the Shuttleworth Collection this aircraft flies regularly throughout the summer months.[4]

Specifications (Mongoose I)

Data from Lumsden.[2][5]

General characteristics

  • Type: 5-cylinder single-row radial
  • Bore: 5 in (127 mm)
  • Stroke: 5.5 in (139.7 mm)
  • Displacement: 540 cu in (8.8 L)
  • Length: 36.6 in (93 cm)
  • Diameter: 45.6 in (116 cm)
  • Dry weight: 340 lb (154 kg)



See also

Related development

Comparable engines

Related lists



  1. Gunston 1989, p. 18.
  2. Lumsden 2003, p. 69.
  3. List from Lumsden
  4. The Shuttleworth Collection - Hawker Tomtit Retrieved: 22 February 2012
  5. Lumsden 2003, Part 4.


  • Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
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